Benthic Foraminiferal Assemblages Research Articles

Changes in the particulate organic carbon pump efficiency since the Last Glacial Maximum in the northwestern Philippine Sea

Changes in bottom and pore water oxygenation over glacial – interglacial cycles have influenced the ocean’s capacity to store particulate organic carbon regardless of its source, either the marine primary productivity or the continent-to-ocean transfer of terrestrial organic matter. In the Philippine Sea, east off Taiwan, despite being currently oligotrophic, the enhanced East Asian Winter Monsoon during the Last Glacial Maximum and the Heinrich Stadial 1 might have altered the nutrient budget in surface waters by providing nutrients from the Eurasian loess dust and deepening the vertical mixing, bringing nutrients from the nutrient-enriched Kuroshio Current subsurface waters to the surface. During the deglaciation, previous studies also suggest an overall weakening of the marine biological pump during the Heinrich Stadial 1, and the rise in sea level is expected to have led to a global significant decline in the ability of continents to bury their particulate organic carbon in marine sediments. However, changes in the continent-ocean transfer of terrestrial organic matter and on the marine biological pump around Taiwan remain poorly constrained.In the present study, we have thus aimed to reconstruct bottom – pore water oxygenation, past marine primary productivity and continental-ocean transfer of terrestrial particulate organic carbon to the ocean since the end of the Last Glacial Maximum, in order to better constrain the ability of marine sediments to capture atmospheric carbon over the past 20,000 years. To this end, sediment core MD18-3523 has been recovered from a levee of Hoping Canyon, north-east of Taiwan, in the Ryukyu forearc basin. The reconstructions were made possible by the application of multivariate statistics and transfer functions on benthic foraminiferal assemblages, by the measurement of total organic carbon concentration and by the investigation of chemical element ratios obtained from X-ray fluorescence (XRF).We observed a transition across the Bølling–Allerød and the Younger Dryas from suboxic-dysoxic bottom – pore waters during Heinrich Stadial 1 to oxic-suboxic during the Holocene, and revealed an increase in marine primary productivity during Heinrich Stadial 1 in all probability due to intensified East Asian Winter Monsoon winds. We have also identified periods of enhanced terrestrial particulate organic carbon transfer to the ocean driven by short-lived extreme events, most likely typhoons, during the Bølling–Allerød, at the beginning of the Early Holocene and the end of the Late Holocene, when the typhoon dynamics affecting Taiwan were intensified. Overall, these findings suggest an enhanced marine biological pump during the Heinrich Stadial 1 and an efficient carbon turbidity pump during the Bølling–Allerød, the Early and Late Holocene, contrasting with the western coast of Taiwan.

Unraveling ecological signals related to the MECO onset through planktic and benthic foraminiferal records along a mixed carbonate-siliciclastic shallow-water succession

The shallow-water Capo Mortola succession (Liguria, NW Italy) yields diverse assemblages of smaller benthic and planktic foraminifera, larger benthic foraminifera (LBF), and calcareous nannofossils. With the aim of improving the understanding of the Middle Eocene Climatic Optimum (MECO) impact on the shallow-water marine biotic communities due to global warming, we provide biostratigraphic and stable isotope data to achieve a reliable stratigraphic constraint of the MECO. The correlation of the stable isotope oxygen data with datasets of similar age from other regions suggests that only the onset of the MECO interval is recorded in the Capo Mortola section. Quantitative analyses of smaller benthic foraminiferal assemblages indicate that the shallow-water setting of Capo Mortola was not particularly affected by the onset of the MECO perturbance because no variation in nutrient supply or oxygen level were detected. A different scenario is recorded by the LBF genera Operculina and Discocyclina, which increased in abundance across the MECO onset, probably due to a rise in temperature and adapting to the increase in nutrient supply. In the upper water column, the variations in calcareous plankton communities appear to be controlled by both the MECO warming and a moderate increase in eutrophic conditions related to the enhanced hydrological cycle. Nutrients, mostly consumed in the upper water column, reached the seafloor in a limited amount, as benthic foraminifera record a meso-oligotrophic environment across the studied MECO interval.

Late Miocene to Early Pliocene paleoceanographic evolution of the Central South Pacific: A deep-sea benthic foraminiferal perspective

The bottom water conditions in the Central South Pacific (CSP) and associated changes in the Lower Circumpolar Deep Water (LCDW) and Antarctic Bottom Water (AABW) under warmer-than-present conditions need to be better understood. These water masses transfer their properties to the major ocean basins. We analyzed Late Miocene to Early Pliocene (5.6–3.6 Ma) marine sediment core sections from the CSP for benthic foraminifera, ice rafted debris (IRD), Ostracoda, planktic foraminifera Orbulina universa abundance, and organic geochemical proxies to assess the bottom water characteristics under warmer-than-present day conditions. A significant increase in IRD abundance between 5.3 and 4.9 Ma marks the Early Pliocene warm phase. The benthic foraminiferal assemblages indicate shifts in bottom water conditions over time in the CSP region. Between 5.6 and 5.3 Ma, predominantly oxygenated bottom water with moderate organic matter flux prevailed. This shifted to suboxic conditions with increased organic matter flux from 5.3 to 4.9 Ma. Subsequently, between 4.9 and 4.4 Ma, bottom water conditions alternated frequently between oxic and suboxic states. Enhanced bottom water formation and inflow of LCDW and AABW in the CSP during 4.4–4.0 Ma promoted oxygenated conditions, accompanied by low organic export flux. However, sluggish bottom water circulation from 4.0 to 3.6 Ma reverted to suboxic conditions, associated with increased carbon burial. Notably, productivity peaked intermittently between 5.3 and 3.6 Ma, as indicated by the occurrence of suboxic species assemblages and increase in the abundance of Orbulina universa, benthic microfauna (ostracods), and other paleoproductivity indicators.

Reconstructing hypoxia on the eastern Arabian sea continental shelf during the past ∼7400 years: A multi-proxy approach

Shallow-sea environmental variations in the eastern Arabian Sea (EAS) have been related to monsoon variability, poorly ventilated intermediate water, and primary productivity changes. To understand these conditions, benthic foraminiferal assemblages, oxygen isotope ratios, and total organic carbon content have been examined in sediment Core SK291/GC13 from the EAS. We aim to retrieve decadal to centennial time-scale changes in past oxygenation and paleoproductivity during the last 7400 calibrated years before the present (cal yr BP). Our proxy data suggest that the oxic benthic foraminifera species were dominant during ∼7400–6000 cal yr BP. The change from oxic to dysoxic occurred during ca. 6000–3500 cal yr BP, and transition from dysoxic to suboxic environmental conditions happened at ca. ∼3500 cal yr BP. These changes are contemporaneous with weakening of the Indian summer monsoon beginning at ∼5500 cal yr BP which culminated into a major arid phase so-called ca 4.2 ka event in the Indian subcontinent. The EAS experienced low productivity during the early phase of our studied interval (∼7400–6000 cal yr BP) and higher productivity in the middle Holocene (6000–3000 cal yr BP), as revealed by the total organic carbon and benthic assemblages. Furthermore, productivity increased in the warm period and decreased in the Little Ice Age on a decadal scale. The spectral analysis of total organic content and suboxic species indicates a 23-year Hale (solar) cycle during the last millennium, indicating a close relationship between solar activity and monsoon variability. The strengthening of the El Nino-Southern Oscillation perhaps amplified due to increased solar activity in the last millennium, which influenced the climate of the EAS. The study highlights paleo-oxygenation shifts based on benthic foraminiferal assemblages, which are crucial for understanding changes in the oxygen minimum zones (OMZs) and their potential impacts on marine ecosystems.

Paleoceanographic Significance of Calcareous Nannofossil Assemblages in the Tropic Shale of Utah during Oceanic Anoxic Event 2 at the Cenomanian/Turonian Boundary

Oceanic Anoxic Event 2 (OAE2) at the Cenomanian/Turonian Boundary (CTB: 93.9Ma) involved the global deposition of organic carbon-rich sediments, a distinctive positive shift in carbon isotope values, and significant species turnover, including changes in calcareous nannofossil assemblages. While it is thought that volcanism triggered organic C-rich sediment deposition during OAE2, it is unclear whether enhanced productivity, increased stratification, of some combination of the two increased organic matter preservation. Calcareous nannofossil assemblages have the potential to qualitatively assess changes in ocean nutrient and temperature conditions to disentangle such ecological dynamics during OAE2. Here we study an expanded section of the Tropic Shale in a drill core in southern Utah near the western margin of the Western Interior Seaway (WIS) to understand how circulation changed during the event and how this may have influenced primary productivity and organic carbon burial. Relative abundance data of well-preserved nannoplankton are complemented with measurements of trace metal, and organic carbon and carbonate concentrations to determine changes in temperature and water column structure, as well as controls on surface water productivity. Detailed statistical analysis helps refine species paleoecologies combined with information from planktic and benthic foraminiferal assemblages and organic biomarkers. Changes in calcareous nannofossil assemblages indicate that near the start of OAE2 the western WIS surface ocean actually cooled for a short time. Following this, surface waters became warmer and more stratified as a Tethyan water mass invaded the seaway. Assemblages suggest that warmth persisted for much of the OAE2 interval, while stratification waxed and waned. The local seaway cooled near the end of OAE2 as Boreal water masses streamed along the western margin. Variations, including the decrease in the abundance of Biscutum constans and short-lived peaks in the abundance of Eprolithus spp. are super regional or possibly global in extent. There is no correlation between calcareous nannofossil assemblages and trace metal concentrations, suggesting they were unaffected by volcanism-related nutrient inputs. Assemblages support other data that suggest increased stratification influenced organic carbon burial in the Western Interior Seaway, and possibly elsewhere, during OAE2.

Upper Eocene benthic foraminiferal assemblages from Western Siberia (Trans-Ural Region): a multi-proxy approach to infer environmental changes

During the Late Eocene, the West Siberian Basin became increasingly isolated from the Peri-Tethys Ocean. The final stage of this marine connection is marked by sediments of the Tavda Formation thatwere deposited during the Bartonian and Priabonion. We have analyzed the composition, structure and diversity of benthic foraminiferal assemblages in core material from the Kyshtyrla Quarry located in the southwest of Western Siberia to reconstruct the depositional environment during the terminal phase of marine sedimentation in theWest Siberian Basin (Upper Tavda Subformation). The foraminiferal record was jointly used with lithological and geochemical multi-proxy data to infer the chronology of events that shaped the critical transition until the complete closure of the basin. Based on stratigraphic index markers, a Priabonian age is indicated for sediments of the Upper Tavda Subformation. From the bottom to the top of the core, the foraminiferal biotas progressively shift from shallow subtidal to low-diverse and stress-tolerant intertidal assemblages, indicative for an increasing isolation of the West Siberian Basin. The increasing shallowing of the marine basin is accompanied by a gradual shift in grain size, and the continuous presence of benthic foraminifera and ratios of geochemical proxies (Sr/Ba, Si/Al, Ti/Al, Zr/Al, K/Al, and U/Th) indicate that mainly marine to brackish water conditions prevailed.

Habitat partitioning and first microplastic detection in the Argentarola marine cave (Tyrrhenian Sea, Italy)

Due to their location, at the boundary between the marine and terrestrial domain, marine caves are very sensitive to environmental changes, but, at the same time, they are extremely vulnerable due to the enclosed setting. Despite their hostile conditions, they are reservoirs of biodiversity, and there is a need to improve their knowledge for conservation and protection purposes. This research studied sediment characteristics (grain size and organic geochemistry) and benthic foraminiferal assemblages of the Argentarola cave (Tuscany, Italy) to define cave ecozones and characterize their environmental variability. Because microplastic pollution is considered a potential threat for the cave, its presence was researched in sediment samples; moreover, the tests of agglutinated foraminifera were analyzed through Fourier Transform Infrared Spectroscopy (FTIR) to verify the possible inclusion of these contaminants.Result indicated the presence in the whole cave of fine-grained sediment with a low organic matter content of clear marine origin, pointing to oligotrophic conditions. Microplastic items at low concentrations were found in sediments, mainly constituted by very small (0.1–0.5 mm) polyethylene and polypropylene fragments and fibers. Foraminifera were abundant and diversified with dominant Spirillina vivipara and Patellina corrugata, like in other small Mediterranean marine caves. Despite the scarce variability of environmental parameters, foraminifera developed two distinct assemblages in relation to sediment texture and organic matter content. In the relatively more organically enriched one, two agglutinated deep-water species, Lagenammina difflugiformis and Glomospira charoides, never recorded before in marine caves, were common. The first one included polyethylene items among the particles of the agglutinated test. Then, this species may be considered an early indicator of microplastic pollution. However, this pollution did not influence the Ecological Quality Status, which was found to be high to good when applying the Foram-Ambi index. This study constitutes a new approach to studying marine caves, providing new tools for the environmental assessment and microplastic monitoring of this protected habitat.

The Badenian/Sarmatian (Middle Miocene) boundary in the Central Paratethys (Kreminna, western Ukraine): Foraminiferal and palynological evidence

The Badenian/Sarmatian boundary in the Paratethys basin, that marks the transition from normal marine to restricted semi-marine conditions due to isolation of the basin from the world ocean at the onset of Sarmatian time, is still far from being fully understood. The Kreminna section is located at the northeastern margin of the Carpathian Foreland Basin (Central Paratethys) in the Medobory Hills region. The Miocene deposits that overlie here the Upper Cretaceous substratum comprise the >1 m thick upper Badenian marls and clays passing upwards into ~4 m thick Sarmatian marly limestones with intercalations of marls, clays and limestones, and >2 m thick limestones in the uppermost part of the exposure. Fifty-three species of benthic foraminifera and four species of planktonic foraminifera have been recorded. Six benthic foraminiferal assemblages are composed almost exclusively of calcareous forms; agglutinated taxa are practically lacking. Elphidium spp., miliolids, Lobatula lobatula and Ammonia spp. are the most common calcareous benthic foraminifera in the material studied. Planktonic foraminifera are represented only by species of Globigerina and occur rarely in the lowermost part of the section. A characteristic feature of palynofacies is the very low proportion of land-derived elements – sporomorphs and cuticles, which suggests a sedimentary setting without terrestrial influx, and taxonomical impoverishment of dinoflagellate cyst assemblages, which are either monospecific or consist mainly of two to three species: in a majority of samples, assemblages with Polysphaeridium zoharyi and P. subtile occur. Most δ18O values range from –1.5 to ~+0.5‰ VPDB and most δ13C values are between 0 and +2‰ VPDB. In general, the δ13C curve mirrors the δ18O changes in the section. The Badenian/Sarmatian boundary is placed at the level where the Cibicidoides ungerianus Assemblage is replaced by the Elphidium fichtelianum Assemblage. At the boundary, planktonic foraminifers and most abundant stenohaline benthic foraminifera disappeared. Bottom waters were well-oxygenated both in the latest Badenian and earliest Sarmatian in the Kreminna location.

Foraminiferal biofacies distribution in the outer channel of Chilika Lagoon, Odisha, India

Benthic foraminiferal assemblages are widely used as a proxy to monitor the coastal environment’s health. The current work involves the seasonal distribution of foraminifera in the outer channel sector of the Chilika Lagoon, Odisha during 2017–2018. The outer channel is marine as the sea mouth is nearby. Altogether 28 species of benthic foraminifera are identified, among which dominant are Ammonia spp. The other calcareous taxa are Elphidium spp, Quinqueloculina sp., Haynesina spp., Pararotalia sp., Hanzawaia sp., Nonionellina sp. and agglutinated forms such as Miliammina sp., Trochammina sp. and Textularina sp. are found in moderate abundance. Based on the pre-monsoon abundance, the cluster analyses show two distinct biofacies zones in the studied area. Total foraminiferal number (TFN) increases during pre-monsoon compared to post-monsoon months. A trend of decreasing abundance was observed in TFN, mainly calcareous taxa towards the inner part of the lagoon, that is, away from the sea mouth.

Spatial and vertical distribution of the genus Amphistegina and its relationship with the indigenous benthic foraminiferal assemblages in the Pelagian Archipelago (Central Mediterranean Sea)

A serious threat affecting the Mediterranean Sea is the migration of Indo-Pacific marine species through the Suez Canal following its opening in 1869. This phenomenon gives extreme causes for concern as many non-indigenous species are highly invasive and seriously threaten native biodiversity. Particularly insidious are small-size taxa such as benthic foraminifera, which are able to invade wide areas un-noticed.The objective of this study is to evaluate the stage of invasion of non-indigenous foraminifer Amphistegina lobifera and the re-colonization of Amphistegina lessonii in two islands of the Pelagian Archipelago (Central Mediterranean) where both species were first recorded in 2005.Absolute abundances quantified in seabed and algal samples collected in 2014 were compared with those detected in 2005 and 2009. Results show that, in the innermost part of the neritic environment, amphisteginids were so abundant and widespread as to have replaced native benthic foraminifera just a few years after earlier reports.On Lampedusa Island, Amphisteginids seem to compete mainly with other symbiont-bearing foraminifera, such as the milioliid Peneroplis pertusus and Peneroplis planatus; we hypothesize that the different algal symbionts housed by the invasive species could play an important role in the invasion success in the Mediterranean Sea. In the most severe case of amphisteginid invasion, as seen around the volcanic island of Linosa, the accumulation of their carbonatic remains is causing a sedimentation switch: increasing the content of white carbonatic sands and replacing the black volcanic substrates, as already observed in Indian Ocean atolls.

Comprehensive Facies Analysis and Depositional Environment Modeling of the Eocene Dammam Formation in Central to Southern Iraq

The Dammam Formation holds immense geological significance, as it spans across a substantial portion of southern Iraq, encompassing a vast area. This formation stands out as the primary aquifer source in the region. To gain a comprehensive understanding of its sedimentology, a comprehensive study was conducted using 310 samples extracted from various boreholes. These boreholes, including Kr-1, Kr-c.q., Nj-20, Ns-13, Ns-24, R-742, and Ru-509. The lithology of the Dammam Formation is limestone, dolomitic limestone, and dolomite rocks, which are also used as raw materials in the manufacture of cement. The microfacies analysis was carried out on Lower-Upper Eocene carbonate rocks along a center-south transect in Iraq. This analysis establishing larger benthic foraminifera enables to reconstruction of the paleoenvironmental model and to show the evolution of a platform along the depth gradient. The analysis revealed the presence of five primary microfacies within the Dammam Formation, each offering unique insights into its composition. These microfacies include Lime-mudstone, Wackestone, Packstone, Floatstone, and Rudstone, all of which contribute to a comprehensive understanding of the formation’s sedimentary makeup. Moreover, this in-depth examination uncovered an additional eight submicrofacies. The benthic foraminiferal assemblages within the Dammam Formation provide valuable insights into the progressive shifts along an ecological gradient, indicating a gradual transition from shallower, more protected (inner) shelf environments to deeper, more open (outer) shelf settings. Within the inner shelf, one can observe the prevalence of orbitolitids, alveolinids, and, to some extent, small miliolids, indicative of this relatively shallow and sheltered environment. Moving towards the inner ramp or shoal region, the foraminiferal composition is characterized by robust nummulitids, signifying the distinctive conditions of this particular zone. From a paleoenvironmental perspective, the Dammam Formation reflects deposition in a diverse range of environments, including peritidal inner ramp areas, lagoons, shoals, restricted-marine platforms, and open marine interior platforms. This variability underscores the complexity of the formation’s geological history and the diverse conditions under which its sediments accumulated over time.

Benthic foraminiferal assemblages in the coastal zone of the yellow river delta: Environmental significance and characteristics of microbial diversity

Unicellular eukaryotes known as benthic foraminifera have sophisticated survival mechanisms and ecological environmental indicators. Ten surface samples from the Yellow River Delta's coastal region were taken for this study to analyze the distribution of foraminifera in relation to environmental factors and to examine their microbial diversity. We looked at the physicochemical aspects of the environment at each sampling site (such as pH, TN, TOC, EC, δ13C, δ15N, PAHs, etc.), and we employed 16S rRNA high-throughput sequencing analysis to look into the interactions between microbial communities and foraminiferal species. The findings demonstrated that the Yellow River Delta's advantage benthic foraminiferal species were Quinqueloculina complanata, Ammonia beccarii, and Ammonia aomoriensis, and that TOC and TN were significant determinants of the distribution of benthic foraminiferal communities. PAH enrichment in the coastal zone effects on microbial communities and benthic foraminifera are not yet readily apparent. Sediment organic carbon and nitrogen isotope analysis revealed that marine plankton may be the dominant source of organic matter in the coastal zone sediments in the research area, which was made up of both land-based and marine organic matter. It implies that foraminifera have some environmental indicators, especially when combined with the distributional traits of the benthic foraminiferal assemblages and their considerable association with environmental parameters. The findings revealed that Q. complanata was found in the Yellow River water-affected estuarine coastal zone, A. aomoriensis was significantly influenced by sediment organic matter content and reflected the estuarine and nearshore environments and the combination of Ammonia beccarii-Ammonia aomoriensis-Elphidium excavatum assemblage indicated a semi-open intertidal shallow marine environment. Additionally, benthic foraminifera showed a responsive association with microorganisms, indicating that microbial diversity may be one of the driving forces behind benthic foraminifera's ability to adjust to environmental changes. The findings of this study will open up new avenues for research into the environmental importance of coastal zone ecosystems and for understanding how benthic foraminiferal communities survive.

A benthic foraminifera perspective of the Late Miocene-Early Pliocene Biogenic Bloom at ODP Site 1085 (Southeast Atlantic Ocean)

The Late Miocene-Early Pliocene Biogenic Bloom (ca. 9.0–3.5 Ma) was a phase of high marine biological productivity documented globally at multiple ocean sites, related to an increase in nutrient input and/or a significant reorganization of nutrients in the oceans. Here, we studied the Biogenic Bloom at Ocean Drilling Program (ODP) Site 1085 in the Southeast Atlantic Ocean, additionally providing an updated age model based on calcareous nannofossil biostratigraphy. During the event, we identified four intervals characterised by distinct benthic foraminiferal assemblages, suggesting changes in paleoenvironmental/paleoceanographic conditions. The Biogenic Bloom extends from 8.1 to 3.0 Ma at Site 1085, as detected by different proxies such as linear sedimentation rates, carbonate mass accumulation rates, benthic foraminiferal indices and assemblage data. The inferred paleoenvironmental changes allowed us to differentiate four intervals within the Biogenic Bloom. From 8.1 to 5.2 Ma and from 3.8 to 3.0 Ma, the high benthic foraminiferal accumulation rates (BFARs) and the abundance of phytodetritus-exploiting taxa point to highly seasonal phytoplankton blooms. Between 5.2 and 4.8 Ma, we document short-term fluctuations between well‑oxygenated conditions with transient input of phytodetritus and phases of low oxygen eutrophic conditions. Between 4.8 and 3.8 Ma, a decrease in opportunistic species and an increase in eutrophic taxa likely suggest a switch to a higher food supply to the seafloor. Our data shows that the onset of the Biogenic Bloom was synchronous with other global well-dated records and its end appears to align with other Atlantic records. Lastly, our findings support the hypothesis that the Biogenic Bloom was not a single productivity event, but a complex event made up of several short-lived, high-productivity regimes with different driving forces.

Boreal (Eemian) Transgression in the Northeastern White Sea Region: Multiproxy Evidence from Bychye-2 Section

Reconstructing interglacial marine environments helps us understand the climate change mechanisms of the past. To contribute to this body of knowledge, we studied a high-resolution 455 cm-thick sediment sequence of the Boreal (Eemian) marine beds directly overlying Moscovian (Saalian) moraine in the Bychye-2 section on the Pyoza River. We analyzed lithological and microfossil (foraminifers, ostracods, pollen, aquatic palynomorphs) variations at the studied site. Stratigraphical zonation is based on the local and well-established regional pollen zones, correlated with the western European pollen zones. The studied marine beds accumulated from the end of the Moscovian glacial (>131 ka) until ca. 119.5 ka. We distinguished three successive phases: a seasonally sea-ice-covered, relatively deep, freshened basin in the initial rapid flooding stage (>131–130.5 ka); a deep basin in the maximum flooding phase with less extensive sea ice cover (130.5–130.25 ka); and a shallow basin with reduced sea ice cover (130.25–119.5 ka). According to a pollen zone comparison with other sites, the regional glacioisostatic rebound started ca. 130 ka. The diverse warm-water assemblages of benthic foraminifers and ostracods containing typical Baltic Sea species occurred during the regression, mainly 128–124 ka, thus giving evidence for a relatively long-lasting connection between the White and Baltic Seas.

Late Miocene to Early Pliocene benthic foraminifera from the Tasman Sea (International Ocean Discovery Program Site U1506)

Abstract. Modern and fossil benthic foraminifera have been widely documented from New Zealand, but detailed studies of material collected from drilling expeditions in the Tasman Sea are scarcer. This study aims to provide an updated taxonomic study for the Late Miocene–Early Pliocene benthic foraminifera in the Tasman Sea, with a specific focus on the paleoceanographic phenomenon known as the Biogenic Bloom. To achieve these goals, we analysed 66 samples from International Ocean Discovery Program (IODP) Site U1506 located in the Tasman Sea and identified a total of 98 taxa. Benthic foraminifera exhibit good preservation, allowing for accurate taxonomic identification. The resulting dataset serves as a reliable and precise framework for the identification and classification of the common deep-water benthic foraminifera in the region. The paleobathymetric analysis based on depth-dependent species indicates deposition at lower bathyal depths. Additionally, the quantitative analysis of the benthic foraminiferal assemblages allowed us to explore their response to the Biogenic Bloom at Site U1506. The paleoenvironmental analysis, focused on the Early Pliocene part of the Biogenic Bloom, points to high-productivity conditions driven by phytoplankton blooms and intensified vertical mixing of the ocean waters. These results provide valuable insights into the paleoceanographic events in the Tasman Sea, particularly the Biogenic Bloom, highlighting the significance of benthic foraminifera as reliable proxies for deciphering paleoenvironmental conditions. The taxonomic identifications and paleoenvironmental interpretations presented herein will aid in future paleoceanographic studies and facilitate comparisons with other deep-sea regions.

Foraminiferal Assemblages As Bioindicators In The Western Caribbean: Albuquerque Cay (Colombia)

Abstract The San Andrés Archipelago (Colombia) constitutes a biological hotspot for the Western Caribbean. However, expanding human populations and unrestrained exploitation of the natural resources jeopardize the sustainability of key ecosystems in most of the islands. We surveyed the benthic foraminiferal assemblages of Albuquerque Cay, a relatively isolated location in the archipelago, during an ecosystem monitoring expedition in 2018. Assemblages recorded from the lagoon and shoreface settings were characteristics of a typical Caribbean reef lagoon. Porcelaneous forms and genera that host algal symbionts, including Archaias, Amphistegina, Heterostegina, Laevipeneroplis, and Sorites, were common, as were smaller taxa, especially Quinqueloculina, Rotorbinella, and Cymbaloporetta were also found in variable proportions, while stress-tolerant and agglutinated taxa were scarce (Elphidium, Clavulina). Results suggest differences in the composition of the assemblages from both sandy cays and the reef lagoon settings, likely conditioned by hydrodynamic fluctuations and nutrient availability. Moreover, a preliminary survey of the FoRAM Index (FI) suggests moderate to good conditions for the environments of Albuquerque Cay, contrasting with estimations of the FI in other insular bodies of the area. Therefore, future studies in the archipelago could reinforce the great potential that foraminiferal assemblages have as bioindicators in this part of the Caribbean.

Benthic Foraminifera as Proxies of Paleoenvironmental Changes in the Sant’Elia-Foxi Canyon (Gulf of Cagliari, Italy, Western Tyrrhenian Sea)

Marine coastal areas are highly dynamic and fragile environments characterised by a complex interplay of biological, physical, and chemical factors. These areas are also affected by anthropogenic activities with the discharge of organic and inorganic contaminants that alters the quality of the environment. In this work, the effects of anthropogenic activities (i.e., urban and industrial development) on benthic foraminifera have been investigated along the A2TM core collected from the Sant’Elia-Foxi Canyon (Gulf of Cagliari, Sardinia—western Tyrrhenian Sea). The Gulf of Cagliari has experienced intense urbanisation since the beginning of the twentieth century with the establishment of petrochemical complexes and harbour activities. The A2TM core, dating from 1907 to 2013, was analysed with an integrated approach that includes grain size, organic matter, and benthic foraminifera characterisation compared with geochemical characterisation. The variations in the composition of the benthic foraminiferal assemblages and the Margalef diversity index are related to the altered environmental conditions that reflect the historical development of the area and to the land-based activities surrounding the Gulf of Cagliari. The statistical analysis identifies two main intervals (i.e., the years 1907–1986 and 1986–2013) that are typified by different benthic foraminiferal assemblages and diversity values. Accordingly, the increases in organic matter content and both organic and inorganic contaminants are well mirrored by a major drop in foraminiferal diversity after 1973 and a major foraminiferal turnover after 1989. The composition of the benthic foraminiferal assemblages in the uppermost part of the core (i.e., 1989–2013) might suggest a lowering of the oxygen availability at the seafloor. These changes might be related to the increase in organic matter and the silty fraction in the same interval likely triggered by damming on land and wetland reclamation.

Changes of bottom water oxygenation during the last half millennium in the Gulf of Tehuantepec (Eastern Tropical North Pacific): A multiproxy approach

The Gulf of Tehuantepec (GoT), in the Eastern Tropical North Pacific Ocean, is home to one of the largest and more intense Oxygen Minimum Zones (OMZ). To identify the OMZ variability during the last five hundred years in the GoT, we analyzed the temporal variations of benthic foraminiferal (BF) assemblages, enrichment of redox-sensitive elements (Mo, V, Cd, U, and Re) and δ15Nsed, on a laminated sediment core. During the Little Ice Age (LIA; ∼1500 to ∼1860 CE), the BF assemblages showed high dominance, and the most abundant BF species in the sediments were Epistominella sandiegoensis, Takayanagia delicata, and Buliminella tenuata. This assemblage can withstand the lowest dissolved oxygen conditions, indicating an intensified OMZ consistent with the enrichment of Mo, Re, Cd, U, and enhanced denitrification. During the Current Warm Period (CWP; ∼1860 CE to present), the BF assemblages were more diverse, and the most abundant species were Bolivina seminuda, Epistominella sp.1, Gyroidina nitidula, and Suggrunda eckisi, an assemblage less tolerant to low dissolved oxygen conditions, together with lower concentrations of redox-sensitive elements and δ15Nsed, suggest weakening of the reducing conditions within the OMZ. Additionally, our BF data showed evidence of the influence of the Pacific Decadal Oscillation on bottom-water oxygenation. Bottom-water oxygenation changes appear to respond to increased solar forcing caused by Intertropical Convergence Zone migration and strengthened Pacific Walker Circulation, which in turn modulated productivity, organic matter flux to the seabed, and oxygen consumption in the bottom water. Our findings agree with previous studies further north from the study site, indicating these changes' regional scale.

Late Paleocene–Early Eocene larger foraminifera from the Galala Plateaus, North Eastern Desert, Egypt: biostratigraphic, paleoenvironmental and paleoecological implications

Two stratigraphic sections are investigated, and a diverse larger benthic foraminiferal assemblage is recorded from the upper Paleocene–lower Eocene Southern Galala Formation at the Galala Plateaus, north Eastern Desert, Egypt. Twenty-eight larger foraminiferal species, belonging to thirteen genera, are identified and their comparative stratigraphic range with the Tethyan zonations of Hottinger (1960) and Serra-Kiel et al. (1998) is documented. Nine shallow benthic zones (SBZ3-6 and SBZ8-12) are designated in the studied interval, involving index zonal markers, e.g., Glomalveolina primaeva (Reichel), G. levis Hottinger, Nummulites atacicus (Leymerie), Alveolina vredenburgi Davies, and A. ellipsoidalis Schwager. Fifty-four thin sections are prepared and analyzed, yielding seven microfacies types in the present study, with larger benthic foraminifera as the dominant biotic components. These microfacies types indicate a deposition in restricted tidal flat inner ramp to open-marine middle ramp environments. The inner ramp environments are dominated by alveolinids, orbitolitids, and in part by miliolids and orthophragminids, reflecting euphotic to mesophotic, meso-oligotrophic, and normal to hyper salinity conditions. The middle ramp environment is characterized by nummulitids, implying meso-oligophotic, oligotrophic, and normal salinity conditions. The studied successions at the Galala Plateaus are devoid of corals in platform stages II and III, similar to the Pyrenean strata from middle latitudes at the northern Tethys, except for small coral patches in both stages in the latter due to the cooler temperature. The Early Eocene (Cuisian) Nummulites accumulations suggest a development on paleohighs in a distal inner ramp environment, and then a transportation by wave and current actions into the surrounding proximal middle ramp environment.

Abundance and distribution of recent benthic foraminifera from the southwestern part of the Bay of Bengal

Foraminifers are ubiquitous and abundant organisms in the marine environment, sensitive to different environmental variables such as pH, dissolved oxygen, salinity, temperature, organic matter and substrate. In the present study, environmental variables and benthic foraminiferal assemblages from 32 surface sediment samples belonging to different water depths were studied to understand the shelf and slope environment of the southwestern Bay of Bengal. Statistical methods such as cluster and principal component analysis (PCA) were used to infer the relationship existing among various foraminiferal assemblages, bathymetry, sediment and bottom water characteristics. Statistical analysis yielded four assemblages, of which assemblage-I is dominated by Nonion faba, Rotalidium annectens, Asterorotalia pulchella, Elphidium crispum, and Amphistegina radiata, and is confined to the shallowest inner shelf region (5 to 35 m water depth) with sandy sediments indicating high-energy condition. Assemblage-II is marked by the abundance of Cibicidoides wuellerstorfi, Hanzawaia concentrica, Quinqueloculina agglutinans, Quinqueloculina seminula, Quinqueloculina lamarckiana, Ammonia beccarri, and Ammonia tepida which are associated with the middle shelf region (water depth 35 to 70 m) with sandy to slightly muddy sand sediments. Assemblage-III is dominated by Asterorotalia dentata, Quinqueloculina venusta, Cancris communis, Cassidulina laevigata, and N. costiferum which occur at a depth of 70 to 170 m in the outer shelf, and are highly associated with slightly muddy sand to muddy sand. Whereas, assemblage -IV includes Uvigerina mediterranea, Bolivina dilatata, Bolivina robusta, and Bulimina marginata foraminiferal species that are abundant in the upper slope (170–244 m water depth) and are confined to muddy sand and sandy mud with low dissolved oxygen in the bottom water. The above assemblages depict that the abundance and distribution of foraminifera are largely controlled by substrate, energy conditions and environmental variables such as temperature, salinity, organic matter and dissolved oxygen.